Harry l



H. L. GRANT PROTECTING DEVICE FOR ELECTRIC DETONATORS Feb. 8 ,.1927. 5

Original Filed Nov. 6. 1924 .flarry L. Grczrzzi 83 1 W I V Elkltozyuua Reissued Feb. 8, 192 7.

UNITED STATES PATENT OFFICE.

HARRY 1.. GRANT, or 'rAM oUA, PENNSYLVANIA, ASSIGNOR TO ATLAS :eownnn. cont- P NY, or WILMINGTON, DELAWARE, A CORPORATION or DELAWARE.

PROTECTING DEVICE FOR ELECTRIC DETONATORS.

Original No. 1,583,922, dated May 11, 1926, Serial No. 748,214, filed November 6, 1924. Application for reissue filed August 13, 1926. Serial No. 129,065.

This invention relates to a protecting device for electric detonators. The primary object of the invention is to provide a device of a simple and inexpensive nature adapted to be applied to the lead in wires of electric detonators and which will serve, while it is in place, to guard against the possibility of the detonator being prematurely exploded by its lead in wires accidentally coming in contact with the source of E. M. F. V

The nature and application of the invention will be readily understood by reference to the accompanying drawing in which:

Figure 1- is an elevation of an electric detonator and its lead in wires, having the device of the present invention applied thereto, and 1 Figure 2 is an enlarged sectional view through the safety device or shunt, illustrating its application to the lead-in wires.

Like numerals designate corresponding parts in both of the figures of the drawing.

Referring to the drawing, 5, designates the casing of an electric detonator and 6 and 7 the usual lead in wires which extend from said casing.

In the ordinary use flow of current of sufiicient strength past point 8 explodes the detonator orciblasting cap. The lead in wires are insulated for some distance from the detonator, as indicated at 6, 7 and the ends of thelead in wires are left bare beyond the-point where the insulation terminates, for ready application to the firing cable leading from a' blasting machine.

In carrying out the present invention, the wires 6 and 7 are preferably crossed so that they touch each other at a point adjacent the termination of the insulation 6, 7 and at this point of contact of the wires the safety device is applied. This device con sists of a softmetal body 9, such as lead for example, which may be pressed into firm,

contact with thefwire, and in turn, hold the cro:sed portions of the wires in intimate contact with each other. When this is done the detonator will be eflectually safeguarded against explosion if the exposed ends of the lead in .wires should accidentally come in contact with a source of electrical energy.-

This is due to the fact that the securing of the wires in intimate contact with each other creates a short circuit at that point. If the of the detonator, the

exposed ends of the wires be accidentally, or otherwise, brought into contact with a source of E. F. of ,sufiicient strength, those portions ofthe wire adjacent the point of contact may fuse and burn off, thereby completely disconnecting the detonator from protecting device in the manner set forth even if the wires were not crossed.

When it is desired to use the detonator the safety device may be stripped therefrom by pulling it longitudinally off the lead in H wires and toward the free ends thereof.

This action not only removes the safety device but, it scrapes and cleans the exposed ends of thewires, leaving them ready for instant attachment to the blasting cable,

Since .theinsulation 6, 7 usually and 7 preferably extends the entire distance from the safety device to the body 5 of the de- *tonator it follows that contact of a source of E. M. F. with that portion of the lead in wires lying between the safety device and the detonator will not result in the explosion of the detonator. However, the device will give anvappreciable and desirable measure 'of protection even if spaced somewhat from the insulation as long as it lies close enough thereto to prevent the creation of such difference of potential between the lead wires under the influence of stray currents, and inwardlyof the point of application of the device, as might explode the detonator.

Assuming the shunt to be spaced far I enough from the insulation so that a source of stray current can be imposed upon the lead wires between the shunt and insulation we would thenjhave a divided path for the current; one from the point of contact of the stray current, on one of the lead wires, around through point- 8 and thence back to the place of beginning but through the other lead wire; andthe other from the point of contact on one wire forwardly through the shunt and back to the place of beginning,

through the other lead wire. The flow of current in these two paths would be inversely proportional to the resistance of such paths and since the shunt, as illuspath therethrough would,

trated, is of a considerable cross sectional area and electrical capacit and since the to start with, it follows that the chancepof creating sufiicient potential difference tobring about accidental explosion of the detonator, would beextremely remote. I wish to make it clear that, ordinarily, I will place the shunt against the insulation and thereby 'avoid all possibility of electrical contacts with the wires rearwardly thereof. However, it is incidentally a fact that the shunt' may be spaced from the insulation and still give an appreciable and desirable measure of protection, for the reasons stated.

ture of Fig-1 constitutes .a

,, that--the detonator will The device of the present invention is of utility at all times between the time of manufacture of the detonator and until the same is actually exploded on the job but it is of particular utility when the detonator 1s being transported and while it is being handled about the work preliminary to the actual firing of a charge. The complete structo the trade. In other words, the structure to be rotected prior to its attachment to a main tiring cable, comprises a detonator and the two lead wires, the inner portions of which are covered with insulation and the outer portions of which are left bare so that the user doesnot haveto expend time in scraping them free of insulation at the time of use." Therefore, the term lead in wires as used in the claims, is intended to mean the wires which are combined with the individual detonators so that the whole constitutes a-unit to be shipped to the trade.

It will be noted that the lead in wires'are inbifilar form which prevents flowof induced currents. This, in conjunction with the safeguard afforded by the creation of the short circuit described, renders it certain not be exploded by stray currents from any source.

' It is to be understood that the invention is not limited to any particular material for the body 9. It is mamfest that any material which willhold the crossed portions of the wires inintimate contactwith each other will carry out the essential object of the invention, viz, to create an electricalcontact at the point of crossing of said wires.

However, I prefer to make the shunt from a soft metal such as lead or the like, in order that the shunt may be pressed firmly around the wires without injuring them in any manner nd also make a more perfect electrical join i.- e. a joint with little or no contact especially if the unit as shipped -fora resistance. By the use of a soft metal the shunt may be pressed on the wires firmly enough to cause it to conform to the sha e of the wires where they pass through 1t, forming a joint similar to a soldered joint. This procedure is made possible by the use of 'a metal which is softer than the metal of which the detonator wires are made. .An-

other advantage of the soft metal shunt is' that the user may readily remove it by simply holding the wire with one hand .and pulling it 011' with the other when ready to fire the shot.

It is to be understood that the invention includes within its purview whatever changes fairly come within either-the terms or the spirit of the appended claims.

Having described my invention, what I claim 1s:

1. The combination with a detonator and its lead in wires having insulation thereon for a portion of their length, of a body embracing'said wires directly at the terminationv of to contact with each other as long as it is in place." I

2. The combination with a detonator and its lead for a portion of their length, of a body embracing the lead in wires directly. at the point of termination of the insulation and holding said wires in crossed and intimate cgntact with each other as long as it is in p ace.

3. A structure as recited in claim 1 wherein said body isof material adapting it to be stripped longitudinally from said wire.

4. The combination with a detonator havg lead in wires which are insulated for a portion of their length, of a soft metal body embracing said wires directly at the point said insulation and holding them in m wires havmg insulation thereon the-lead in wires having insulation thereon cuit, with stray electric current or conductors carrying electric current, and so made and applied, that the act of stripping the shunt from the terminal wires cleans the ex-,

posed ends of the said wires. I 7. An electrical detonator in which a being adapted to be portion of their length, of a soft metal shunt made of a metal softerthan that from which the terminal wires of the detonator are made, is placed squarely against the insulation of the terminal wires of the said electrical detonator.

' 8. The combination with a having bifilar lead wires, said lead wires having a covering of insulating material thereon for a portion oftheir length, outwardly, and bein bare therebeyond, to provide' means for'attachment of the detonator to the common firing cable of a blasting machine, of a body mounted upon and electrically connecting said lead wires, close5eno'ugh to the point of termination of the insulating materialto prevent the creation of a difier-. ence of potential between the lead wires rearwardly thereof, to thereby protect the detonator from explosion under the infludetonator,-

enceof an accidentally imposed M. F.

9. The combination with a detonator haying the bifilar lead wires, individual there to, said wi res being insulated for a portion of their length outwardly and being bare therebeyond, of a body of vconductive material uniting said wires at such point with respect to the termination of the insulation as to prevent-the creation of such difi'erence inpotential in the detonator as to cause the premature explosion of the detonator under the influence of accidental or stray currents.

In testimony whereof, I aifix my signature. a

HA RY L. G ANT, 

